The only bees without a sting (or at least reduced) i can think of now, are those of the subfamily Meliponinae (tropic & neotropic distribution). Thatswhy they called "stingless bees". Camargo et al. (1992) published a mini-review on the subfamily: http://www.apidologie.org/index.php?opt ... RT0003.pdf

But he doesnt really explain why those bees evolved that way. I also dont know any other literature really dealing with this question.

This topic got me thinking, what other aculeates are there that have lost their sting? Certain ant subfamilies (at least Dolichoderinae and Formicinae) and Chrysididae(?) come to mind, but are there some other groups as well?

I don't know about the exact reason why those bees lost their sting, but if i remember correctly, Meliponini use their exocrine glands as defensive weapon, so perhaps the sting has become useless that way...

I'm not sure if theres more Group which lost their sting. Also not sure why they lost it. In case of the Chrysididae i would expect that it evolved like it ist now because of their parasitic nature. They dont hunt a prey, they just have to lay an egg into the host cell.cheersEckart

Sadly it seems i have erred about chrysidids, they have the sting after all:

Morgan 1984 wrote:Despite the developement of this specialised egg placement system, the Chrysiddiae have still retained the sting apparatus. Its effectiveness is certainly reduced as the telescope tube bends in Chrysis ignita when the sting unsuccessfully tries to penterate human skin (personal observation).

This is actually extremely interesting subject, so i will try to dig up and read some literature about this for sure. If i find something interesting or worthwhile, i will post my findings into this topic.

Well, since they had a sting in the past u can still find remnants. E.g. in Hedychrum they are bigger, but in Chrysis there is not much left. Chrysididae also only have 3-4 abdominal segments heavily sclerotized and visible from outside, the others are reduced and inside and partly used to form the flexible tube to lay eggs. of the sting itself there is only the very tips left. But they are not really sclerotized very much anymore and probably without a very important function. As they dont need it and as they also dont need the Stingapparatus (muscles/venom) the selective pressure is off thse structures, so they got reduced. I would compare it to some legless lizzards where u still can find small remnants of the leg-bones if u check out the scleleton.

So the cuckoo wasps have lost or "lost" their sting, but the general trend at least among bees seems to be selection for stronger and bigger stings for nest parasites (e.g. Psithyrus). Interestingly, Michener (2000) says that bees with the most reduced sting apparatus are Dioxyini, which are parasitic... Michener also says that some Andrenidae have reductions in their sting and accompanying organs.

Perhaps the telescopic ovipositor (and their ability to roll into tight ball*) have enabled / forced the reduction of the sting in the chrysidid lineage?

[Edit: * this part has to be false, because "lower" chrysids like Amiseginae and Cleptinae cannot(?) roll into ball and still have their stings atrophied(?). Perhaps the ballrolling ability evolved in Chrysidinae, because they coudn't anymore use their sting but had to do something to deter the pissed nest owners they faced at host nests...]

With reguards to Chrysidids would it not be more ecologically sensible of them to simply roll up when caught by a host, or otherwise simple survive the irate host's attack without any aggressive response. In this way once they escape the nest the host goes back about their business and builds and provisions another nest that can be parasitized in due course, which would not happen if it was killed or mortally wounded during the Chrysidids escape.